A power semiconductor device is used for a switching circuit and an inverter circuit for power control.
The power semiconductor device is required to have a high breakdown voltage and a low on-resistance, and a breakdown voltage and an on-resistance of a power semiconductor device using silicon (Si) are reaching limits based on a physical characteristic of Si.
On the other hand, since a band gap of a nitride semiconductor is wider than that of Si, a semiconductor device using the nitride semiconductor may realize a characteristic having both a lower on-resistance and a higher breakdown voltage when compared with the semiconductor device using silicon.
Due to miniaturization of a field effect transistor (FET) using a nitride semiconductor, a length of a gate of the FET is shortened, and thus a current easily flows between a source and a drain. This phenomenon is referred to as a short channel effect. Improvement in controllability of a threshold voltage of the FET is desired to suppress this short channel effect.